Ferric pseudobactin 358 as an iron source for carnation

The influence of the siderophore produced by plant growth‐promoting Pseudomonas putida strain WCS358, pseudobactin 358 (PSB358), on chlorophyll synthesis and iron(III) reduction in carnation cultivars Lena and Pallas grown in hydroponics was studied. Ferric pseudobactin 358 (4 μM) stimulated chlorophyll synthesis in cv. Lena, but not in cv. Pallas. FeEDDHA stimulated chlorophyll synthesis in both cultivars. Differences between the two carnation cultivars in the utilization of FePSB358 as an iron source are correlated with differences in iron efficiency reactions of the two cultivars: Fe‐deficient plants of cv. Lena produced more and longer root hairs than Fe‐deficient plants of cv. Pallas, and the ferric reducing activity of cv. Lena was higher than that of cv. Pallas.     

A comparative analysis of element composition of roots and leaves of barley seedlings grown in the presence of toxic cadmium,molybdenum, nickel,and zinc concentrations 1

Barley seedlings were grown in hydroponic culture in the presence of toxic concentrations of cadmium (Cd), molybdenum (Mo), nickel (Ni), and zinc (Zn) and analyzed for element composition [boron (B), calcium (Ca), Cd, iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), phosphorus (P), and Zn]. In a first survey, heavy metal concentrations were selected which resulted in a similar inhibition of root growth. Toxic concentrations of Cd, Mo, Ni, and Zn revealed both similar and distinct effects on specific leaf and root element contents. Examples for such responses were decreasing contents in root Mn and Mg at elevated levels of all heavy metals, including Mo, in the medium. In contrast, changes in root contents of B were specific for the applied type of heavy metal stress. The heavy metal dependent changes in B, Ca, Mg, and Mn contents were studied in more detail. In some cases, severe heavy metal toxicity caused excessive accumulation or depletion of nutrient elements that may be deleterious to the plants in addition to other primary damages caused by the heavy metal ions.     

Public and Private Employers’ Perceptions of the Competence of Botswana College of Agriculture Graduates

A large sample size technique was used to select 30 employers each from the private and public sector to examine their perception of the competence of agricultural graduates. Data were collected with a structured questionnaire and analyzed using means, standard deviation, and t test. The results show that, for 16 crop production tasks, public agroemployers were favorably disposed to competence in 4 tasks, while private employers were not favorably disposed to competence in any tasks. Both public and private employers were not favorably disposed to competence in farm engineering tasks. The Botswana College of Agriculture curriculum should be overhauled to better prepare graduates for employment.     

Knowledge Levels and Perceived Effect of Climate Change on Extension Delivery in North West Province,South Africa

A simple random sampling technique was used to select 20% of the extension officers in North West Province, South Africa. Data on knowledge levels and perceived effect of climate change on extension delivery were collected and analyzed using frequency counts, percentages, and multiple regression analysis. The results show that a wide range of knowledge levels exists on climate change issues related to causes, effect, vulnerability, and mitigation and that extension officers will have to address new skill requirements for farmers, the need for specialized extension services, and changing and diversified livelihoods. The results have several implications for training and educating extension officers on climate change issues.     

Waste Recycling through Composting in Nigeria

While some composting had been practiced on a limited basis in Nigeria 50 years ago, the practice still is largely neglected. Farmers find it more convenient to use fertilizers because of the ease of carrying, storing and applying. However, since 1986, there has been a major change in the composition of refuse in Nigeria. With greater numbers of people in the low socioeconomic groups scavenging on the refuse dumps collecting paper, metal, glass and plastics, the remaining refuse is mostly organic and ideal for making compost. Studies undertaken at the University of Ibadan reveal that once mobilized, communities can be effective in launching composting projects. Appropriate technology is favored in processing the wastes rather than extensive and, often unaffordable, mechanization.     

Impact on Water Quality of High and Low Density Applications of Spent Mushroom Substrate to Agricultural Lands

We studied the influence of spent mushroom substrate (SMS) land application on water resources. Four study sites, including mushroom farms with low or high density land applications of SMS, and two controls, an alfalfa field and a woodland, were instrumented with soilwater lysimeters and groundwater monitoring wells. Water samples were collected during the dormant season (winter) and growing season (spring). Samples were analyzed for a number of water quality parameters, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonia, chloride, nitrate, nitrite, phosphate, sulfate, aluminum, cadmium, calcium, chromium, copper, iron, lead, magnesium, manganese, mercury, nickel, potassium, silicon, sodium, and zinc. Additional analyses were performed for pesticides commonly used in the cultivation of alfalfa or corn, or for insect control, including methomyl, dimethoate, hexazinone, atrazine, diuron and permethrin.

All agricultural sites had elevated salt concentrations relative to the woodland site. The mushroom farm where SMS was applied in high concentrations had salt concentrations in the soilwater that were 10 to 100 times higher than the other agricultural sites. Of particular note were ammonium, nitrate, chloride, sulfate, calcium, magnesium, sodium, and potassium. Each of these were also elevated in the groundwater. The high salt concentrations were reflected in measurements of electrical conductivity. DOC and DON concentrations were also elevated in the soilwater and groundwater. Groundwater from each agricultural site, including the agricultural control, exceeded the primary drinking water standard for nitrate.

No pesticide residues were detected in well or lysimeter water collected at either site amended with SMS. Water samples collected from the woodland and at the alfalfa field not receiving SMS contained part per trillion quantities of a few pesticides.     

Soot in urban atmospheres: determination by an optical absorption technique

We have used the high optical absorptivity of urban and source particulates to trace their "graphitic" component. The optical absorptivity and the particulate carbon loading show a strong correlation. Analyses of the data indicate that primary soot emissions compose a major fraction of the carbonaceous aerosol and put a low limit on secondary organic material produced in correlation with the ozone concentration.     

Germinate to exterminate: chemical stimulation of Spongospora subterranea resting spore germination and its potential to diminish soil inoculum

Hoagland's solution (HS), a defined nutrient supplement for plants, has been previously reported to stimulate zoospore release from resting spores of the potato pathogen Spongospora subterranea f. sp. subterranea. This study obtained direct empirical evidence for an increase in zoospore release with HS treatment, and identified Fe‐EDTA as the stimulant component of HS. Stimulation of resting spores by HS and Fe‐EDTA resulted in greater and earlier zoospore release compared to a distilled water control, and in the presence of a susceptible tomato host plant resulted in enhanced root infection. Given the labile nature of S. subterranea zoospores, it was postulated that stimulation of premature release of zoospores from the dormant resting spores in absence of susceptible hosts could reduce soil inoculum levels. In two glasshouse trials in the absence of host plants, both Fe‐EDTA and HS soil treatments reduced S. subterranea soil inoculum levels, providing proof of concept for the ‘germinate to exterminate’ approach to inoculum management.     

Effects of Restricted Feeding Regimes on Growth and Feed Utilization of Juvenile Gilthead Sea Bream, Sparus aurata

The effect of restricted feeding on growth, feed efficiency, and body composition was studied in juveniles of gilthead sea bream, Sparus aurata. Juveniles (6.4 g) were stocked into 12 tanks at a density of 16 fish per tank. Four different feeding schedules were tested on triplicate groups of juvenile fish: (1) control fed for 48 d without deprivation, (2) starvation for 1 d and then refed for 2 d (S1), (3) 50% satiation for 2 d and then refed to apparent satiation for 2 d (R2), and (4) 50% satiation for 6 d and then refed to apparent satiation for another 6 d (R6). Results indicated that all fish subjected to cycled restricted feeding regimes were unable to achieve catching up with control group. The specific growth rate of fish in the control was significantly higher than those in S1, R2, and R6, which were not significantly different from each other. Protein efficiency and protein productive value were significantly higher in R2 compared to control, S1, and R6. Fish in R2 had lowest feed conversion ratio (1.12) compared to the control (1.17). Body protein composition in R6 was less than that of the control, S1, and R2, while moisture, lipid, and ash content were not significantly different compared to the control.